DRA Laboratories

Welcome to the home page of DRA Laboratories and theMLSSA Acoustical Measurement System.

MLSSA 10WI Rev 9 and MLSSA SPO 4WI Rev 9 Released

MLSSA version 10WI Rev 9 will run under Windows XP for analysis-only of measurements stored on disk. MLSSA was also updated to conform to the latest specification for Male and Female STI measurements according to IEC 60268-18 Third Edition (2003-03).

MLSSA SPO version 4WI Rev 9 was updated to automatically switch the MLSSA RCAI into impedance mode. This feature allows you to automatically switch between T/S measurements of driver parameters and normal acoustic frequency response measurements using a microphone.

Many other new software features were added to MLSSA and MLSSA SPO. A list of all new features with full descriptions can be found in the

downloaded and installed at no charge by owners of MLSSA versions 10WI or higher.
The MLSSA, MLSSA SPO and MLSSA RCAI reference manuals were also been updated and are now available online in PDF file format. See below under Online Documentation. Note that Acrobat Reader's search function can be used to quickly search the PDF manuals.

MLSSA 2000 Mothercard Upgrade

The MLSSA 2000 mothercard features a pink-filtered MLS output for improved SNR in the bass region.

Theory of Upsampled Digital Audio

Upsampling has become a boon to audiophiles who hear significant and sometimes dramatic improvements in the sound quality of CDs played back through commercially available upsampling digital-to-analog conversion products. A great deal of confusion surrounds this advance in digital audio reproduction. The paper published here defines the process of upsampling and presents a scientific explanation of its effects upon digital audio sound quality.

Product Literature

MLSSA is the industry standard loudspeaker measurement system and the MLSSA Speaker Parameter Option (SPO) is the industry standard for measuring the Thiele-Small parameters of loudspeaker drivers. MLSSA and SPO both include QC (Quality Control) PASS/FAIL functions for high-speed automated production line testing of loudspeakers and drivers. Other important applications of MLSSA include speech intelligibility measurements according to IEC 60268-16 Third Edition via the Speech Transmission Index (STI) and Rapid Speech Transmission Index (RASTI) as well as room acoustics measurements according to ISO 3382. For details, see the MLSSA Acoustical Measurement System and MLSSA Speaker Parameter Option brochures below.